first of all is the Pump too much for this setup? I dont think so.
Eheim 1260/1060, 600 gph
It will be in this setup
Maze 4-1 226 watt pelt CPU
Maze 4-1 80 watt pelt GPU
1972 Chevy Impala Heatercore
Res with 2 inlets 1/2 and a 1" outlet to fit the pump
Since it will be split, this pump should work way better than a Eheim 1250, right? Or will it just be a total waste.